Electronic circuit design relies heavily on the use of integrated circuits (ICs), circuits in which all components, passive and active, are integrated on a single semiconductor substrate. Integrated circuit performance is affected not only by internal factors, such as tolerances associated with semiconductor fabrication techniques, but is likewise influenced by external factors, such as the impedance associated with external circuits and connections. For example, the impedance, sometimes referred to as “contact resistance”, associated with a connection of the integrated circuit to an external device, such as a power supply of Automatic Test Equipment (ATE), can significantly affect the integrated circuit performance. Elevated contact resistance can indicate a complete failure of a particular integrated circuit connection (i.e., a broken lead wire or solder connection) and even less significantly elevated contact resistance can degrade integrated circuit performance. For example, some integrated circuit functions require a minimum supply voltage and a high contact resistance can result in an insufficient supply voltage level at the integrated circuit for certain circuit functionality.
One technique for measuring external impedance in a test environment is a manual process whereby a supply voltage coupled to the integrated circuit is set at a first level while the current and voltage at a particular IC connection is measured, such as with a Kelvin connection. The supply voltage is thereafter set to a second level while the current and voltage at the same connection is measured and the ratio of the difference between the voltages and currents measured at the two supply voltage levels is computed to provide an indication of the contact resistance. However, this technique for measuring external impedance tends to be slow and labor intensive and therefore costly to the overall IC manufacturing process.